From 18bc19a7aa4cd08d45d64f6741b8b1e0f48f262b Mon Sep 17 00:00:00 2001 From: Richard Sandiford Date: Wed, 22 Aug 2018 13:02:48 +0000 Subject: [PATCH] [2/2] Fix bogus inner induction (PR 86725) This patch is the second part of the fix for PR 86725. The problem in the original test is that for: outer1: x_1 = PHI ; ... inner: x_2 = PHI ; ... x_3 = ...; ... outer2: x_4 = PHI ; ... there are corner cases in which it is possible to classify the inner phi as an induction but not the outer phi. The -4.c test is a more direct example. After failing to classify x_1 as an induction, we go on to classify it as a double reduction (which is basically true). But we still classified the inner phi as an induction rather than as part of a reduction, leading to an ICE when trying to vectorise the outer phi. We analyse the phis for outer loops first, so the simplest fix is not to classify the phi as an induction if outer loop analysis said that it should be a reduction. The -2.c test is from the original PR. The -3.c test is a version in which "wo" really is used a reduction; this was already correctly rejected, but for the wrong reason ("inner-loop induction only used outside of the outer vectorized loop"). The -4.c test is another way of tickling the original problem without relying on the undefinedness of signed overflow. The -5.c test shows an (uninteresting) example in which the patch prevents a spurious failure to vectorise the outer loop. 2018-08-22 Richard Sandiford gcc/ PR tree-optimization/86725 * tree-vect-loop.c (vect_inner_phi_in_double_reduction_p): New function. (vect_analyze_scalar_cycles_1): Check it. gcc/testsuite/ PR tree-optimization/86725 * gcc.dg/vect/no-scevccp-pr86725-2.c: New test. * gcc.dg/vect/no-scevccp-pr86725-3.c: Likewise. * gcc.dg/vect/no-scevccp-pr86725-4.c: Likewise. * gcc.dg/vect/no-scevccp-pr86725-5.c: Likewise. From-SVN: r263774 --- gcc/ChangeLog | 7 ++++ gcc/testsuite/ChangeLog | 8 +++++ .../gcc.dg/vect/no-scevccp-pr86725-2.c | 23 ++++++++++++ .../gcc.dg/vect/no-scevccp-pr86725-3.c | 25 +++++++++++++ .../gcc.dg/vect/no-scevccp-pr86725-4.c | 23 ++++++++++++ .../gcc.dg/vect/no-scevccp-pr86725-5.c | 24 +++++++++++++ gcc/tree-vect-loop.c | 35 +++++++++++++++++++ 7 files changed, 145 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-2.c create mode 100644 gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-3.c create mode 100644 gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-4.c create mode 100644 gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-5.c diff --git a/gcc/ChangeLog b/gcc/ChangeLog index 63779d362c2..c5515e4c038 100644 --- a/gcc/ChangeLog +++ b/gcc/ChangeLog @@ -1,3 +1,10 @@ +2018-08-22 Richard Sandiford + + PR tree-optimization/86725 + * tree-vect-loop.c (vect_inner_phi_in_double_reduction_p): New + function. + (vect_analyze_scalar_cycles_1): Check it. + 2018-08-22 Richard Sandiford PR tree-optimization/86725 diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog index 3117afaa82d..55312e89897 100644 --- a/gcc/testsuite/ChangeLog +++ b/gcc/testsuite/ChangeLog @@ -1,3 +1,11 @@ +2018-08-22 Richard Sandiford + + PR tree-optimization/86725 + * gcc.dg/vect/no-scevccp-pr86725-2.c: New test. + * gcc.dg/vect/no-scevccp-pr86725-3.c: Likewise. + * gcc.dg/vect/no-scevccp-pr86725-4.c: Likewise. + * gcc.dg/vect/no-scevccp-pr86725-5.c: Likewise. + 2018-08-22 Richard Sandiford PR tree-optimization/86725 diff --git a/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-2.c b/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-2.c new file mode 100644 index 00000000000..b208c1a2d61 --- /dev/null +++ b/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-2.c @@ -0,0 +1,23 @@ +/* { dg-do compile } */ +/* { dg-additional-options "-O -w" } */ + +int +nr (int xe) +{ + int oo, wo = 0; + + for (oo = 0; oo < 4; ++oo) + { + int qq; + + for (qq = 0; qq < 2; ++qq) + { + wo += 0x80000000; + xe += wo; + } + } + return xe; +} + +/* { dg-final { scan-tree-dump "reduction used in loop" "vect" { target vect_int } } } */ +/* { dg-final { scan-tree-dump-not "OUTER LOOP VECTORIZED" "vect" } } */ diff --git a/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-3.c b/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-3.c new file mode 100644 index 00000000000..590c744be0c --- /dev/null +++ b/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-3.c @@ -0,0 +1,25 @@ +/* { dg-do compile } */ +/* { dg-additional-options "-O -w" } */ + +int foo; +int +nr (int xe) +{ + int oo, wo = 0; + + for (oo = 0; oo < 4; ++oo) + { + int qq; + + for (qq = 0; qq < 2; ++qq) + { + wo += 0x80000000; + xe += wo; + } + } + foo = wo; + return xe; +} + +/* { dg-final { scan-tree-dump "reduction used in loop" "vect" { target vect_int } } } */ +/* { dg-final { scan-tree-dump-not "OUTER LOOP VECTORIZED" "vect" } } */ diff --git a/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-4.c b/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-4.c new file mode 100644 index 00000000000..d995c9b30fe --- /dev/null +++ b/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-4.c @@ -0,0 +1,23 @@ +/* { dg-do compile } */ +/* { dg-additional-options "-O -w" } */ + +int +nr (unsigned int xe, unsigned int qqn) +{ + unsigned int oo, wo = 0; + + for (oo = 0; oo < 4; ++oo) + { + unsigned int qq = qqn; + do + { + wo += 1; + xe += wo; + } + while (qq-- > 0); + } + return xe; +} + +/* { dg-final { scan-tree-dump "reduction used in loop" "vect" { target vect_int } } } */ +/* { dg-final { scan-tree-dump-not "OUTER LOOP VECTORIZED" "vect" } } */ diff --git a/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-5.c b/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-5.c new file mode 100644 index 00000000000..6e7c9d8a77b --- /dev/null +++ b/gcc/testsuite/gcc.dg/vect/no-scevccp-pr86725-5.c @@ -0,0 +1,24 @@ +/* { dg-do compile } */ +/* { dg-additional-options "-O -w" } */ + +unsigned int foo; +int +nr (unsigned int xe, unsigned int qqn) +{ + unsigned int oo, wo = 0; + + for (oo = 0; oo < 4; ++oo) + { + unsigned int qq = qqn; + do + { + wo += 1; + xe += qq; + } + while (qq-- > 0); + } + foo = wo; + return xe; +} + +/* { dg-final { scan-tree-dump "OUTER LOOP VECTORIZED" "vect" { target vect_int } } } */ diff --git a/gcc/tree-vect-loop.c b/gcc/tree-vect-loop.c index f21d995fdb9..d5e35521cef 100644 --- a/gcc/tree-vect-loop.c +++ b/gcc/tree-vect-loop.c @@ -462,6 +462,40 @@ vect_is_simple_iv_evolution (unsigned loop_nb, tree access_fn, tree * init, return true; } +/* Return true if PHI, described by STMT_INFO, is the inner PHI in + what we are assuming is a double reduction. For example, given + a structure like this: + + outer1: + x_1 = PHI ; + ... + + inner: + x_2 = PHI ; + ... + x_3 = ...; + ... + + outer2: + x_4 = PHI ; + ... + + outer loop analysis would treat x_1 as a double reduction phi and + this function would then return true for x_2. */ + +static bool +vect_inner_phi_in_double_reduction_p (stmt_vec_info stmt_info, gphi *phi) +{ + loop_vec_info loop_vinfo = STMT_VINFO_LOOP_VINFO (stmt_info); + use_operand_p use_p; + ssa_op_iter op_iter; + FOR_EACH_PHI_ARG (use_p, phi, op_iter, SSA_OP_USE) + if (stmt_vec_info def_info = loop_vinfo->lookup_def (USE_FROM_PTR (use_p))) + if (STMT_VINFO_DEF_TYPE (def_info) == vect_double_reduction_def) + return true; + return false; +} + /* Function vect_analyze_scalar_cycles_1. Examine the cross iteration def-use cycles of scalar variables @@ -522,6 +556,7 @@ vect_analyze_scalar_cycles_1 (loop_vec_info loop_vinfo, struct loop *loop) } if (!access_fn + || vect_inner_phi_in_double_reduction_p (stmt_vinfo, phi) || !vect_is_simple_iv_evolution (loop->num, access_fn, &init, &step) || (LOOP_VINFO_LOOP (loop_vinfo) != loop && TREE_CODE (step) != INTEGER_CST)) -- 2.30.2